Molecular and serological detection of A. centrale- and A. marginale-infected cattle grazing within an endemic area

A reverse line blot hybridization (RLB) one-stage nested PCR (nPCR) for Anaplasma centrale and a nested PCR for Anaplasma marginale were used to detect infected cattle grazing within an endemic region in Israel. A novel set of PCR primers and oligonucleotide probes based on a 16S ribosomal RNA gene was designed for RLB detection of both Anaplasma species, and the performance of the molecular assays compared. The immunofluorescent antibody test (IFA) was used to detect antibodies to both Anaplasma species, whereas, a highly sensitive and specific competitive enzyme-linked immunosorbent assay (cELISA) was used to detect antibodies in A. centrale-vaccinated cattle. The RLB and the nested PCR procedures showed bacteremia with sensitivity of 50 infected erythrocytes per milliliter. Up to 93% of the A. centrale vaccinates carried specific antibodies that were detected by cELISA, and up to 71% of the vaccinated cattle were found to be naturally infected with A. marginale according to the PCR and the RLB assays. Nevertheless, no severe outbreaks of A. marginale infection occurred among vaccinated herds in this endemic region. It appears that both, molecular tools and serology are useful for evaluation of the vaccine efficacy. In the light of wide natural field infection with A. marginale, strong recommendations to continue the A. centrale vaccination program regime will continue until a new generation of non-blood-based vaccine will be developed.

Transcription analysis of the major antigenic protein 1 multigene family of three in vitro-cultured Ehrlichia ruminantium isolates

Ehrlichia ruminantium, an obligate intracellular bacterium transmitted by ticks of the genus Amblyomma, causes heartwater disease in ruminants. The gene coding for the major antigenic protein MAP1 is part of a multigene family consisting of a cluster containing 16 paralogs. In the search for differentially regulated genes between E. ruminantium grown in endothelial and tick cell lines that could be used in vaccine development and to determine if differences in the map1 gene cluster exist between different isolates of E. ruminantium, we analyzed the map1 gene cluster of the Senegal and Gardel isolates of E. ruminantium. Both isolates contained the same number of genes, and the same organization as found in the genome sequence of the Welgevonden isolate (H. Van Heerden, N. E. Collins, K. A. Brayton, C. Rademeyer, and B. A. Allsopp, Gene 330:159-168, 2004). However, comparison of two subpopulations of the Gardel isolate maintained in different laboratories demonstrated that recombination between map1-3 and map1-2 had occurred in one subpopulation with deletion of one entire gene. Reverse transcription-PCR on E. ruminantium derived mRNA from infected cells using gene-specific primers revealed that all 16 map1 paralogs were transcribed in endothelial cells. In one vector (Amblyomma variegatum) and several nonvector tick cell lines infected with E. ruminantium, transcripts were found for between 4 and 11 paralogs. In all these cases the transcript for the map1-1 gene was detected and was predominant. Our results indicate that the map1 gene cluster is relatively conserved but can be subject to recombination, and differences in the transcription of map1 multigenes in host and vector cell environments exist.

Point seroprevalence survey of Ehrlichia ruminantium infection in small ruminants in The Gambia

Using the MAP1-B enzyme-linked immunosorbent assay, we tested 1,318 serum samples collected from sheep and goats at 28 sites in the five divisions of The Gambia to determine the Ehrlichia ruminantium seroprevalence rates and to assess the risk for heartwater. About half (51.6%) of 639 sheep were positive, with seroprevalence rates per site varying between 6.9% and 100%. The highest seroprevalence was detected in the western part of the country (88.1% in the Western Division and 62.1% in the Lower River Division). Sheep in the two easterly divisions (Central River and Upper River divisions) showed the lowest seroprevalence of 29.3% and 32.4%, respectively, while those in the North Bank Division showed an intermediate prevalence of 40.6%. In goats, less than one-third (30.3%) of 679 animals tested were positive. The highest seroprevalence was detected in goats in the North Bank Division (59%) and Western Division (44.1%). Goats in the Lower River Division showed an intermediate level of 21.9%, whereas the lowest rates were found in the eastern part of the country (4.8% in the Central River Division and 2.3% in the Upper River Division). At nearly all sites, seroprevalence rates were higher in sheep than in goats. The results show a gradient of increasing heartwater risk for susceptible small ruminants from the east to the west of The Gambia. These findings need to be taken into consideration when future livestock-upgrading programs are implemented.

Validation of the indirect TaSP enzyme-linked immunosorbent assay for diagnosis of Theileria annulata infection in cattle

An ELISA based on a recombinant Theileria annulata surface protein (TaSP) was evaluated for detection of antibodies in sera from cattle exposed to tropical theileriosis in Sudan. The reference positive samples, used in this study, were from Theileria-infected populations and consisted of 80 cattle from an endemic area in Khartoum State, with high antibody titers in the indirect fluorescent antibody test (IFAT). The reference negative samples were taken from non-exposed populations and consisted of 120 cattle maintained under strict tick control at a commercial farm in Sudan. The cut-off value determined by Two-Graph Receiver-Operating Characteristic (TG-ROC) curves was set at 31.6%, based on the positive reference samples. Further diagnostic validation was performed, which consisted of the measurement of the area under the ROC (AUC) and by valid range proportion (VRP), which was 0.97 and 0.98 for the cut-off, respectively. There were no cross-reactions with antibodies raised against Babesia spp. It is concluded that the TaSP ELISA is a useful test for the diagnosis of T. annulata infection in cattle under field conditions.

Preliminary survey of ticks (Acari: Ixodidae) on cattle in northern Sudan

In a cross sectional survey conducted during the period June 2001 to July 2002, the geographical distribution of ticks on cattle in the Sudan was determined. Seventeen locations were surveyed from Northern, Central, Eastern, Western, Blue Nile and White Nile Provinces. Total body collections of ticks were made from 20 cattle at each location. Four tick genera and 11 species were identified. The tick species collected included Amblyomma lepidum, Amblyomma variegatum, Boophilus decoloratus, Hyalomma anatolicum anatolicum, Hyalomma dromedarii, Hyalomma impeltatum, Hyalomma marginatum rufipes, Hyalomma truncatum, Rhipicephalus evertsi evertsi, Rhipicephalus sanguineus group and Rhipicephalus simus simus. Major ecological changes have occurred due to extensive animal movement, deforestation, desertification and establishment of large mechanized agricultural schemes. These factors have certainly affected the distribution of ticks and tick-borne diseases in the Sudan. The absence of A. variegatum and A. lepidum in northern Sudan was not surprising, since these tick species are known to survive in humid areas and not in the desert and semi-desert areas of northern Sudan. The absence of B. annulatus in northern and central Sudan is in accordance with the finding that this tick species is restricted to the southern parts of the central Sudan. The presence of H. anatolicum anatolicum in Um Benin in relatively high abundance is an interesting finding. The present finding may indicate that the southern limit of this species has changed and moved southwards to latitude 13 degrees N. It is concluded that major changes in tick distribution have taken place in the Sudan.

Autochthonous canine babesiosis in The Netherlands

Outbreaks of autochthonous babesiosis, caused by Babesia canis, occurred in The Netherlands in the spring and autumn of 2004 affecting 23 dogs. Nineteen animals recovered after treatment, whereas four dogs died. Adult Dermacentor reticulatus ticks collected from these dogs indicate that canine babesiosis could become endemic in The Netherlands.

Endemic stability for Theileria parva infections in Ankole calves of the Ankole ranching scheme, Uganda

A population-based study was carried out on the Ankole ranching scheme in south-west Uganda with the aim of determining the endemic status of Theileria parva infections. For this purpose, the age-related sero-prevalence of T. parva and the specific calf mortality associated with the parasite were assessed. Blood samples were collected from 931 Ankole calves of up to 12 months of age from 81 randomly selected herds. The relationship between rainfall pattern and whole-body Rhipicephalus appendiculatus counts was determined. The influence of tick control practices on East Coast fever-related calf mortality, and sero-positivity were also determined. A significant (r2 = 0.76, P = 0.000) association between R. appendiculatus counts and rainfall was observed. There was no significant (P > 0.05) association between theileriosis-related calf mortality, sero-positivity and the different tick control practices. Antibody prevalence based on the PIM ELISA was above 70% among calves of 6 months of age in 96% in all the herds. Theileria parva-related calf mortality determined by repeated herd visits and farm records ranged between 0 % and 5.4 %. It was concluded that endemic stability for theileriosis, caused by T. parva, existed in the study area, and that the risk of the occurrence of economically important outbreaks of East Coast fever in indigenous cattle was regarded as minimal under the prevailing conditions.

[Autochthonous babesiosis in dogs in The Netherlands associated with local Dermacentor reticulatus ticks]

In the spring and autumn of 2004, 20 respectively 3 cases of autochthonous canine babesiosis were diagnosed in the Netherlands, four of which ended fatally. Adult Dermacentor reticulatus ticks were found on four dogs. Case descriptions and diagnostics of this B. canis outbreak are discussed in more detail.

The genome of the heartwater agent Ehrlichia ruminantium contains multiple tandem repeats of actively variable copy number

Heartwater, a tick-borne disease of domestic and wild ruminants, is caused by the intracellular rickettsia Ehrlichia ruminantium (previously known as Cowdria ruminantium). It is a major constraint to livestock production throughout subSaharan Africa, and it threatens to invade the Americas, yet there is no immediate prospect of an effective vaccine. A shotgun genome sequencing project was undertaken in the expectation that access to the complete protein coding repertoire of the organism will facilitate the search for vaccine candidate genes. We report here the complete 1,516,355-bp sequence of the type strain, the stock derived from the South African Welgevonden isolate. Only 62% of the genome is predicted to be coding sequence, encoding 888 proteins and 41 stable RNA species. The most striking feature is the large number of tandemly repeated and duplicated sequences, some of continuously variable copy number, which contributes to the low proportion of coding sequence. These repeats have mediated numerous translocation and inversion events that have resulted in the duplication and truncation of some genes and have also given rise to new genes. There are 32 predicted pseudogenes, most of which are truncated fragments of genes associated with repeats. Rather then being the result of the reductive evolution seen in other intracellular bacteria, these pseudogenes appear to be the product of ongoing sequence duplication events.

Confirmation of occurrence of Babesia canis vogeli in domestic dogs in South Africa

The prevalence of Babesia infections in domestic dogs in South Africa was studied using reverse line blot hybridization and 18S sequence analysis. Babesia canis vogeli was confirmed for the first time in domestic dogs in South Africa. Out of a total of 297 blood samples collected from domestic dogs in Bloemfontein, East London, Johannesburg, Durban and from the Onderstepoort Veterinary Academic Hospital, 31 were positive for Babesia canis rossi, whereas B. c. vogeli was detected in 13 dogs. None of the dogs carried both parasites. The detection of B. c. vogeli has implications with regard to prevalence and varied clinical manifestation of canine babesiosis in South Africa.

On molecular taxonomy: what is in a name?

Gene sequences of small portions of the genome are often used for premature detailed taxonomic changes, neglecting polyphasic taxonomy, which should also consider phenotypical characteristics. Three examples are given: (i) Recently, members of the genera Eperythrozoon and Haemobartonella have been moved, correctly so, from the Rickettsiales to the Mycoplasmatales, but were assigned to the genus Mycoplasma, mostly on the basis of 16S rRNA sequence analysis. Not only is the 16S rRNA sequence similarity between 'classical' Mycoplasma and these species of Eperythrozoon and Haemobartonella less than that between some other well-recognised bacterial genera, but their biological differences amply justify their classification in different genera of the Mycoplasmatales. Furthermore, the move creates considerable confusion, as it necessitates new names for some species, with more confusion likely to come when the 16S rRNA sequences of the type species of Eperythrozoon, a name which has priority over Mycoplasma, will be analysed. (ii) In the Rickettsiales, members of the genera Anaplasma, Ehrlichia, Cowdria, Neorickettsia and Wolhbachia are so closely related phylogenetically on the basis of 16S rRNA sequences, and for some also of groESL operon sequences, that they have recently been fused, correctly so, into one family, the Anaplasmataceae, while the tribes Ehrlichieae and Wolbachieae have been abolished. Sequence diversity within the 'classical' genus Ehrlichia has led to classifying E. phagocytophila (including E. equi and the agent of human granulocytic ehrlichiosis), E. platys and E. bovis in the genus Anaplasma, while others have been retained in Ehrlichia, which also includes Cowdria ruminantium. E. sennetsu and E. risticii have been transferred to the genus Neorickettsia. 16S rRNA and GroEL sequences of 'classical' Anaplasma and some members of 'classical' Ehrlichia do show a close relationship, but differences in citrate synthase gene sequences, the GC content of this gene, and sequences of the gene encoding the beta-subunit of RNA polymerase, not to speak of the phenotypical differences, do not justify the fusion into one genus. Because of the phylogenetical diversity in Ehrlichia it is recommended that a new genus name be created for the E. phagocytophila genogroup (and E. platys and E. bovis). (iii) One of the conclusions of studies on the phylogeny of ticks of the subfamilies Rhipicephalinae and Hyalomminae, based on nucleotide sequences from 12S rRNA, cytochrome c oxidase I, the internal transcribed spacer 2, 18S rRNA, as well as morphological characters, is that Boophilus should be considered as a subgenus of Rhipicephalus. While Boophilus and Rhipicephalus are undoubtedly close, the obviously important morphological and biological differences between the genera Rhipicephalus and Boophilus are thus overruled by similarities in the sequences of a number of genes and this leads to considerable confusion. Polyphasic taxonomy amply justifies maintaining Boophilus as a separate genus, phylogenetically near to Rhipicephalus. This note is a plea for a cautious and balanced approach to taxonomy, taking into account molecular genotypical information, as far as is possible from different genes, as well as phenotypical characteristics.

Simultaneous detection and differentiation of Theileria and Babesia parasites infecting small ruminants by reverse line blotting

Characteristic sequence signatures were identified within the hypervariable region 4 (V4 region) of the small ribosomal RNA gene of ovine/caprine piroplasm species including Theileria lestoquardi, T. ovis, T. separata, Babesia ovis, B. motasi, B. crassa [comprising strains B. crassa (Iran) and B. crassa (Turkey)] and several novel species: Theileria sp. 1 (China), Theileria sp. 2 (China) and Babesia sp. (China), [comprising strain Babesia sp. (Lintan), and Babesia sp. (Ningxian)] as defined previously. Based on the ascertained gene variations a reverse line blotting (RLB) assay was developed enabling direct, concurrent, highly specific and sensitive identification of virtually all presently known ovine/caprine piroplasm species. All probes bound to their respective target sequence only, therefore, no cross-reaction was observed resulting in clear recognition of either individual strains, species or groups. No signal was observed when ovine and caprine genomic DNA was used as the control, demonstrating that the signals are due to the presence of parasite DNA in investigated samples. Furthermore, the sensitivity of RLB could be considerably enhanced to detect a parasitemia level of at least 10(-12)% by reamplification of PCR products (nested PCR) thereby substantially increasing the possibility of identifying carrier animals.

Phylogeny of sheep and goat Theileria and Babesia parasites

The phylogenetic relationship of Theileria and Babesia species infecting sheep and goats on the basis of their 18S RNA gene structure was addressed in the present study. For this purpose, the complete sequences of the small ribosomal RNA genes of a panel of sheep and goat piroplasm isolates, including T. lestoquardi, T. ovis, T. separata, B. ovis, B. motasi, B. crassa and several novel species, were sequenced and compared. The classification based on the established phylogenetic tree corresponded with traditional systematics and revealed that sheep/goat piroplasm species are of polyphyletic origin. The independent evolution of almost all sheep/goat piroplasms suggests that speciation may have occurred after transfer of the piroplasm-transmitting tick from a primal wild ruminant host to domestic sheep and goats. In accordance with recent reports, our study confirms the existence of at least two additional sheep/goat piroplasm species, designated Theileria sp. 1 (China) and Theileria sp. 2 (China). The recently reported pathogenic sheep/goat Theileria sp. 1 (China) seems to be identical with a Theileria sp. isolated from Japanese serow. Furthermore, our results suggest that T. ovis represents a single species.

Detection by two enzyme-linked immunosorbent assays of antibodies to Ehrlichia ruminantium in field sera collected from sheep and cattle in Ghana

Two serological tests for detection of antibodies to Ehrlichia (previously Cowdria) ruminantium, the causative agent of heartwater, were compared by using field sera collected from sheep and cattle as part of serosurveys in Ghana. Sera selected as either negative or positive by a new polyclonal competitive enzyme-linked immunosorbent assay (PC-ELISA) were tested by the indirect MAP1-B ELISA. Cutoff values of 14 percent positivity (14 PP) for both ruminant species were obtained for the MAP1-B ELISA by using preseroconversion Ghanaian sera and were compared with previously recommended cutoff values of 29 PP for sheep and 38 PP for cattle. With the 14-PP cutoff, of 151 sheep sera which tested negative by PC-ELISA, 89% were also negative by MAP1-B ELISA, while of 419 sheep sera positive by PC-ELISA, 98% were also positive by MAP1-B ELISA. Of 261 bovine sera negative by PC-ELISA, 82% were also negative by MAP1-B ELISA. Of 511 bovine sera positive by PC-ELISA, only 47% were positive by MAP1-B ELISA; these included 168 sera collected from cattle following first seroconversion as detected by both tests, with 125 of these sera positive by PC-ELISA but only 59 and 5 positive by MAP1-B ELISA with the 14- and 38-PP cutoff levels, respectively. These results indicate that both assays are highly sensitive and specific for detection of E. ruminantium exposure in sheep but that the MAP1-B ELISA lacks sensitivity for postseroconversion bovine sera in comparison to the PC-ELISA. Both tests confirm E. ruminantium seroprevalence of at least 70% in Ghanaian sheep; levels of exposure among Amblyomma variegatum-infested Ghanaian cattle are likely to be higher than the seroprevalence value of 66% obtained with the PC-ELISA.

A fatal case of human babesiosis in Portugal: molecular and phylogenetic analysis

We report the first case of human babesiosis in Portugal. A 66-year-old splenectomized man was admitted to a Lisbon hospital after 1 week of fever, abdominal pain, anorexia and nausea. A high parasitaemia (30%) of Babesia parasites was found in Giemsa-stained blood smears and, despite treatment, the patient died several weeks later of renal failure. Ethylenediaminetetraacetic acid blood samples were processed for polymerase chain reaction (PCR) and reverse line blot hybridization to confirm and characterize the Babesia infection. The amplified PCR product was cloned and subsequently sequenced. Molecular analysis showed that the infection was caused by Babesia divergens and that other blood parasites were not involved. Phylogenetic analysis showed that the 18 S ribosomal RNA gene sequence was similar to three other European isolates of B. divergens. In view of the high risk for splenectomized individuals, strict measures should be taken to avoid tick bites.

Babesia bicornis sp. nov. and Theileria bicornis sp. nov.: tick-borne parasites associated with mortality in the black rhinoceros (Diceros bicornis)

A novel Babesia species, designated Babesia bicornis sp. nov., was identified in three black rhinoceroses (Diceros bicornis) that died in wildlife areas in Tanzania and South Africa. Screening of black rhinoceroses in South Africa revealed, in addition to B. bicornis, a second parasite, designated Theileria bicornis sp. nov.

Simultaneous detection of Anaplasma and Ehrlichia species in ruminants and detection of Ehrlichia ruminantium in Amblyomma variegatum ticks by reverse line blot hybridization

The detection of Anaplasma and Ehrlichia species is usually based on species-specific PCR assays, since no assay is yet available which can detect and identify these species simultaneously. To this end, we developed a reverse line blot (RLB) assay for simultaneous detection and identification of Anaplasma and Ehrlichia species in domestic ruminants and ticks. In a PCR the hypervariable V1 region of the 16S ribosomal RNA (rRNA) gene was amplified with a set of primers unique for members of the genera Anaplasma and Ehrlichia [Int. J. Syst. Evol. Microbiol. 51 (2001) 2145]. Amplified PCR products from blood of domestic ruminants or Amblyomma variegatum tick samples were hybridized onto a membrane to which eight species-specific oligonucleotide probes and one Ehrlichia and Anaplasma catch-all oligonucleotide probe were covalently linked. No DNA was amplified from uninfected blood, nor from other hemoparasites such as Theileria annulata, or Babesia bigemina. The species-specific probes did not cross-react with DNA amplified from other species. E. ruminantium, A. ovis and another Ehrlichia were identified by RLB in blood samples collected from small ruminants in Mozambique. Finally, A. variegatum ticks were tested after feeding on E. ruminantium infected sheep. E. ruminantium could be detected in adult ticks even if feeding of nymphs was carried out 3.5 years post-infection. In conclusion, the developed species-specific oligonucleotide probes used in an RLB assay can simultaneously detect and identify several Ehrlichia and Anaplasma species. However, as no quantitative data for the detection limit are available yet, only positive results are interpretable at this stage.

Susceptibility of bovine umbilical cord endothelial cells to bovine herpesviruses and pseudocowpox virus

The purpose of the study was to determine the susceptibility of bovine umbilical cord endothelial (BUE) cells to bovine herpesvirus (BHV) 1, BHV2, BHV4 and BHV5, and to pseudocowpox virus. The detection limits and growth curves of these viruses in BUE cells were compared with those in Vero, Madin-Darby bovine kidney (MDBK). or bovine fetal diploid lung (BFDL) cells. Detection limits were determined by inoculating cell cultures with serial 10-fold dilutions of these viruses, and growth curves by titration of virus, harvested at various times after infecting cells at a multiplicity of infection of 0.1. The detection limits of BHV2 and BHV4 were lower in BUE cells than in Vero or MDBK cells, and cytopathic effects were observed earlier in BUE cells. In addition, BHV2 and BHV4 grew to higher titres in BUE cells than in Vero or MDBK cells. BUE cells appeared to be equally susceptible to BHV5, but less susceptible to BHV1.1 and BHVI.2 than MDBK cells. The study showed that BUE cells are highly susceptible to BHV2 and BHV4. and that the use of BUE cells can improve the laboratory diagnosis of these viruses. The use of BUE cells could also improve the isolation and growth of pseudocowpox virus.

The phylogenetic position of the Theileria buffeli group in relation to other Theileria species

Theileria parasites known as either T. buffeli, T. orientalis or T. sergenti share many characteristics and are referred to as the T. buffeli group. The 18S ribosomal RNA and merozoite-piroplasm surface protein-encoding genes display a wider genetic variation within the T. buffeli group than between well defined species like T. annulata and T. parva. Analysis of 18S rRNA gene sequences from the database showed that similar groups of related Theileria parasites occur in wild ruminants in Japan and the USA. Moreover, a recently discovered Theileria species pathogenic for small ruminants in China is phylogenetically related to these Japanese Theileria parasites. Phylogenetic analysis of all Theileria 18S rRNA genes reported thus far allowed a subdivision into eight clusters. Some of these clusters contain multiple different species, whereas others appear to contain parasites with similar biological properties whose true speciation remains at present unresolved. The consequences for 18S rRNA based diagnostic assays is discussed.

Ticks and tick-borne diseases in Asia with special emphasis on China

An international conference on the control of ticks and tick-borne diseases sponsored by the European Commission was held in Shanghai between 11 and 15 September 2000. Participants from China, Europe, Australia, India, Iran, Israel, Japan and Thailand attended the meeting. The main objectives were: (1) determining the current situation concerning the epidemiology, economics, diagnosis and integrated control measures of ticks and tick-borne diseases caused by protozoan and rickettsial pathogens; (2) the creation of regional and international research networks and priority settings; (3) the creation of training possibilities for young scientists; (4) the identification of new research directions and priority settings in relation to vaccine development and diagnostics. The papers presented during this meeting focused on parasite characterisation and the description of yet unidentified Theileria and Babesia species pathogenic for large and small ruminants in China. In addition, progress made in immunity and vaccine development against the pathogens mentioned above and their vector ticks was also discussed.

Transmission of an unidentified Theileria species to small ruminants by Haemaphysalis qinghaiensis ticks collected in the field

The transmission of a recently identified Theileria species pathogenic for sheep and goats in northern China is described. Haemaphysalis qinghaiensis nymphs which had been collected from grass in epidemic areas were able to transmit this Theileria species to sheep. The pathogen was also transmitted to sheep and goats by three batches of adult ticks collected from grass, ticks collected when moving about on sheep and ticks which were found partially engorged on sheep or goats.

Characterisation of the 33kDa piroplasm surface antigen of Theileria orientalis/sergenti/buffeli isolates from West Java, Indonesia

The immunodominant 33/35kDa antigen of a Theileria isolate from West Java, Indonesia, was characterised and immuno-affinity purified by use of a monoclonal antibody, KUL-a4, and was shown to be representative of the T. orientalis/sergenti/buffeli group. The aminoterminal sequence of the purified 35kDa peptide (20 residues) was determined by automated Edman degradation and found to correspond to the predicted amino acid sequence of a prospective p33 gene previously sequenced from the same isolate. The cleavage site of a putative signal peptide was identified and conforms the (-3, -1) rule for signal peptidases. The existence of dimeric and trimeric forms of the p33/35 antigen is hypothesised from Western blot profiles. KUL-a4 appeared specific for the T. orientalis/sergenti/buffeli group. It did not recognise in indirect fluorescence antibody test (IFAT), intraerythrocytic bodies of Anaplasma marginale or piroplasms and schizonts of T. mutans, T. parva and T. annulata, whereas cattle antisera raised to these species showed cross-reactivity in IFAT. It however, appeared weakly cross-reactive in Western blot and ELISA, with the 34kDa piroplasm antigen of one T. annulata (Gharb) isolate. The present study indicates that the isolated antigen belongs to the p33/34 antigen family described within the T. sergenti/orientalis/buffeli group, and documents the group-specificity of one of its epitopes.

Transcriptional analysis of the major antigenic protein 1 multigene family of Cowdria ruminantium

The major antigenic protein 1 (MAP1) of the tick-borne rickettsial pathogen Cowdria ruminantium is encoded by a multigene family containing conserved and variable genes. The part of a locus containing the map1 multigene family that was characterized contained three homologous, but non-identical map1 genes, designated map1-2, map1-1, and map1. Reverse transcriptase-polymerase chain reaction was used to study the transcriptional activity of these genes in isolates of C. ruminantium grown in bovine endothelial cells, in two different tick cell lines, and in Amblyomma variegatum ticks. The map1 gene was always transcribed, whereas transcription of map1-2 was not detected under any of the tested conditions. The map1-1 gene transcript was detected in A. variegatum ticks, but was not found in virulent C. ruminantium Senegal grown in bovine endothelial cells at 30 or 37 degrees C. Interestingly, transcripts of map1-1 were also found in different passages of the in vitro attenuated Senegal isolate grown in bovine endothelial cells, as well as in the Gardel isolate grown in two tick cell lines. When transcribed, map1-1 was present on a polycistronic messenger together with map1.

Seasonal epidemiology of ticks and aspects of cowdriosis in N'Dama village cattle in the Central Guinea savannah of Côte d'Ivoire

In the Central Guinea savannah of Côte d'Ivoire, cattle breeding started only approximately 30 years ago. The impact of parasitism on the overall health status and productivity of the trypanotolerant N'Dama cattle in this area is unknown. In close collaboration with national veterinary institutions and local farmers, we studied spectrum, burden and seasonal dynamics of ticks (including aspects of cowdriosis) on N'Dama village cattle. In a longitudinal study, three randomly selected cattle herds (traditional farming type) of one village were examined repeatedly for ticks. Spectrum, burden, seasonal epidemiology of ticks were assessed. In these traditional herds (which lack (ecto)parasite management), all animals were infested by ticks at monthly counts. Five different tick species were identified; the four genera in order of frequency were: Amblyomma (overall prevalence 96%), Boophilus (47%), Hyalomma (<1%) and Rhipicephalus (<1%). Amblyomma variegatum was the most-abundant tick on cattle in all seasons. Seroprevalence of Cowdria ruminantium was 31% (95% CI: 26, 36%). Most of the animals typically carried low tick burdens. N'Dama cattle seem well adapted to their environment and can resist the tick burdens under this traditional farming system.

Study of Theileria annulata population structure during bovine infection and following transmission to ticks

Tams1 is the polymorphic immunodominant merozoite-piroplasm surface protein of Theileria annulata. Evidence for selection of divergent forms of Tams1 has been obtained recently. This study was performed to address whether selection takes place during persistent infection of the bovine host or during passage through the Hyalomma tick vector. Four calves were infected with a T. annulata isolate representing multiple parasite genotypes. The development of the parasite population was analysed by denaturing gradient gel electrophoresis (DGGE) using the Tams1 gene as a marker. In addition, the parasitaemia was measured by a semi-quantitative reverse line blot hybridization assay in order to correlate Tams1 variation to changes in parasitaemia. It was found that both parasitaemia and parasite population displayed limited variation during persistent infection. Ticks were allowed to acquire T. annulata during 2 periods of the bovine infection. Tams1 alleles detected in ticks fed during acute infection were identical to the population in the bovine host. However, ticks fed during the carrier status acquired parasites showing a single Tams1 isotype that represented, in several cases, a minor population in the bovine host at the time of infestation. Although only a limited number of ticks were studied, these preliminary data suggest that specific parasite genotypes may be selected during tick transmission from a carrier animal.

Detection of haemoparasites in cattle by reverse line blot hybridisation with a note on the distribution of ticks in Sicily

A reverse line blot hybridisation (RLB) of 21 oligonucleotides with polymerase chain reaction (PCR) amplified regions of 16S rRNA (Ehrlichia/Anaplasma group) or 18S rRNA (Babesia/Theileria group) genes of haemoparasites detected Theileria annulata, T. buffeli/orientalis, Babesia bovis, B. bigemina, B. divergens, Ehrlichia bovis, Anaplasma marginale, A. centrale and unknown species within the Rickettsia tribe.A very high prevalence of mixed infections was detected, which indicated that animals infected with Babesia spp. were also infected with Theileria spp. and/or Anaplasma spp. The tick distribution appeared to be seasonal with Hyalomma marginatum as the most frequently observed tick and Boophilus annulatus and Ixodes ricinus as the least frequently observed ticks. Other species identified in the 818 ticks collected during the five sampling periods between April 1998 and November 1999 included H. lusitanicum, Rhipicephalus sanguineus group, R. bursa, Dermacentor marginatus, Haemaphysalis punctata, B. annulatus and I. ricinus.

Dynamics of IgG1 and IgG2 subclass response in dogs naturally and experimentally infected with Ehrlichia canis

Immunoglobulin (Ig) G subclasses were measured in dogs naturally and experimentally infected with Ehrlichia canis using enzyme-linked immunosorbant assay (ELISA). In this study, a higher IgG2 subclass response was noticed to natural and experimental E. canis infection in dogs. Anti-E. canis-IgG2 optic density (OD) values were found to be significantly higher than anti-E. canis-IgG1 during the different phases of the disease, and no differences in the IgG subclass responses to E. canis infection were found between symptomatic and asymptomatic dogs. Doxycycline treatment, which eliminated the rickettsia in three of four persistently infected dogs, had no noticeable influence on the E. canis-IgG subclass OD values during the treatment period. In order to facilitate the study, an ELISA for the detection of anti-E. canis IgG was developed and was shown to be sensitive and specific for E. canis-IgG, and in a significant correlation with the indirect immunofluorescence antibody test.

Heartwater (Cowdria ruminantium infection) as a cause of postrestocking mortality of goats in Mozambique

A serological survey in Mozambique to detect antibodies to Cowdria ruminantium, the etiologic agent of heartwater, revealed a seroprevalence of 8.1% (n = 332) for goats in the northern province of Tete and of 65.6% (n = 326) for goats in the southern provinces. Translocation of 10 serologically negative goats from Tete to farms in the south resulted in two clinical cases of heartwater that were fatal. In addition, four goats seroconverted within the study period of 5 weeks. One goat showed no symptoms. Two goats died of other causes, whereas the remaining goat went missing after 1 week. Experimental needle infections of goats and sheep were conducted to confirm results and to isolate different strains of C. ruminantium. These data indicate that translocation of goats from the north to the south of Mozambique bears a high risk of C. ruminantium infection, which can cause fatal disease.

Antibody responses to MAP 1B and other Cowdria ruminantium antigens are down regulated in cattle challenged with tick-transmitted heartwater

Serological diagnosis of heartwater or Cowdria ruminantium infection has been hampered by severe cross-reactions with antibody responses to related ehrlichial agents. A MAP 1B indirect enzyme-linked immunosorbent assay that has an improved specificity and sensitivity for detection of immunoglobulin G (IgG) antibodies has been developed to overcome this constraint (A. H. M. van Vliet, B. A. M. Van der Zeijst, E. Camus, S. M. Mahan, D. Martinez, and F. Jongejan, J. Clin. Microbiol. 33:2405-2410, 1995). When sera were tested from cattle in areas of endemic heartwater infection in Zimbabwe, only 33% of the samples tested positive in this assay despite a high infection pressure (S. M. Mahan, S. M. Samu, T. F. Peter, and F. Jongejan, Ann. N.Y. Acad. Sci 849:85-87, 1998). To determine underlying causes for this observation, the kinetics of MAP 1B-specific IgG antibodies in cattle after tick-transmitted C. ruminantium infection and following recovery were investigated. Sera collected weekly over a period of 52 weeks from 37 cattle, which were naturally or experimentally infected with C. ruminantium via Amblyomma hebraeum ticks, were analyzed. MAP 1B-specific IgG antibody responses developed with similar kinetics in both field- and laboratory-infected cattle. IgG levels peaked at 4 to 9 weeks after tick infestation and declined to baseline levels between 14 and 33 weeks, despite repeated exposure to infected ticks and the establishment of a carrier state as demonstrated by PCR and xenodiagnosis. Some of the serum samples from laboratory, and field-infected cattle were also analyzed by immunoblotting and an indirect fluorescent-antibody test (IFAT) to determine whether this observed seroreversion was specific to the MAP 1B antigen. Reciprocal IFAT and immunoblot MAP 1-specific antibody titres peaked at 5 to 9 weeks after tick infestation but also declined between 30 and 45 weeks. This suggests that MAP 1B-specific IgG antibody responses and antibody responses to other C. ruminantium antigens are down regulated in cattle despite repeated exposure to C. ruminantium via ticks. Significantly, serological responses to the MAP 1B antigen may not be a reliable indicator of C. ruminantium exposure in cattle in areas of endemic heartwater infection.

Integrated molecular diagnosis of Theileria and Babesia species of cattle in Italy

A reverse line blot hybridization (RLB) test was developed to specifically identify six Theileria spp. (T. annulata, T. parva, T. mutans, T. velifera, T. taurotragi, and T. buffeli/orientalis) and three Babesia spp. (B. bovis, B. bigemina, and B. divergens). No cross reaction was observed with other livestock pathogens (such as Anaplasma marginale, A. centrale, A. ovis, Cowdria ruminantium, Trypanosoma brucei, T. congolense, and T. vivax). This method was used to test bovine blood samples collected in Sicily in April and November, 1998. Preliminary results indicated that T. annulata and T. buffeli/orientalis were the main species observed in cattle blood. Babesia species represented 1.8% and 23.5% in April and November, respectively.

Characterization of attenuated Theileria annulata vaccines from Spain and the Sudan

Theileriosis caused by Theileria annulata can be effectively prevented by vaccination with attenuated, cultured schizonts. Although these attenuated vaccines have been applied for a long time, not much is known about the fate of the vaccine strain in the field. Here, two experimental Spanish vaccine strains originating in Cádiz and Cáceres, and one Sudanese strain are studied to address the development of a carrier status and the infectivity for Hyalomma ticks. Moreover, the heterogeneity of the merozoite surface protein, Tams1, was analyzed in search for an attenuation marker. Using the sensitive reverse line blot (RLB) hybridization, the development of a low level carrier status was demonstrated in the Cáceres and Sudanese line vaccinated calves. Although no signal was detected in the Cádiz line vaccinated calves, seroconversion against the schizont stage was observed, as it was in all other calves. The experimental transmission of T. annulata by Hyalomma ticks to naïve calves was unsuccessful for all cell line inoculated calves. Tams1 heterogeneity indicated a clonal selection of parasites during the process of attenuation, but the Tams1 sequence itself has no connection with the attenuation status. In conclusion, a carrier status develops in attenuated schizont culture vaccinated calves, but is not infective for Hyalomma ticks. Based on these data, the risk for spread of the vaccine strains in the field may be very low.

Significance of serological testing for ehrlichial diseases in dogs with special emphasis on the diagnosis of canine monocytic ehrlichiosis caused by Ehrlichia canis

Dogs are susceptible to a number of ehrlichial diseases. Among them, canine monocytic ehrlichiosis is an important and potentially fatal disease of dogs caused by the rickettsia Ehrlichia canis. Diagnosis of the disease relies heavily on the detection of antibodies and is usually carried out using the indirect immunofluoresence antibody (IFA) test. The IFA test may be confounded by cross-reactivities between a number of the canine ehrlichial pathogens. This article presents a review of the ehrlichial diseases affecting dogs with reference to their immune responses, host specificities, cross-reactivites and diagnosis. Diagnostic means such as Western immunblot, dot-blot and PCR are discussed. The use of the IFA test as a diagnostic means for E. canis is presented along with its potential pitfalls. The review emphasizes that the disease process, cross-reactivites with other ehrlichial species, multiple tick-borne infections and persistent IFA antibody titers post-treatment, should all be considered when interpreting E. canis serological results.

Evidence for the utility of the Bm86 antigen from Boophilus microplus in vaccination against other tick species

The Bm86 antigen, as originally identified in Boophilus microplus, is the basis of commercial tick vaccines against this tick species. The potential for using this antigen or homologues of the antigen in vaccination against other tick species has been assessed. We have conducted vaccine trials in cattle using the B. microplus-derived recombinant Bm86 vaccine (TickGARD) using pairs of vaccinated calves and control calves. These were infested with B. microplus and Boophilus decoloratus larvae simultaneously. For both species, the numbers of engorged female adult ticks, their weight and egg-laying capacity were all reduced, leading to a reduction in reproductive capacity of 74% for B. microplus and 70% for B. decoloratus. Hyalomma anatolicum anatolicum ticks were fed both as immatures as well as adults on vaccinated calves and non-vaccinated controls. There was an overall 50% reduction in the total weight of nymphs engorging on vaccinated calves, and a suggestion of a subsequent effect on feeding adults. For Hyalomma dromedarii there was a 95% reduction in the number of nymphs engorging and a further 55% reduction in weight of those ticks surviving. Rhipicephalus appendiculatus and Amblyomma variegatum ticks were fed simultaneously both as immatures and subsequently as adults. There was no evidence for a significant vaccination effect. Finally, the amino acid sequence of a Bm86 homologue found in H. a. anatolicum unequivocally demonstrated the conservation of this molecule in this species. Our strategy for the development of multivalent anti-tick vaccines is discussed in relation to these findings.

Generation of a mosaic pattern of diversity in the major merozoite-piroplasm surface antigen of Theileria annulata

The polypeptide Tams1 is an immunodominant major merozoite piroplasm surface antigen of the protozoan parasite Theileria annulata. Generation and selection of divergent antigenic types has implications for the inclusion of the Tams1 antigen in a subunit recombinant vaccine or use in the development of a diagnostic ELISA. In this study a total of 129 Tams1 sequences from parasites isolated in Bahrain, India, Italy, Mauritania, Portugal, Spain, Sudan, Tunisia and Turkey were obtained to estimate the extent of Tams1 diversity throughout a wide geographical range. Significant sequence diversity was found both within and between isolates and many of the sequences were unique. No geographical specificity of sequence types was observed and almost identical sequences occurred in different geographical areas and a panmictic population structure is suggested by our results. A sliding window analysis identified sub-regions of the molecule where selection for amino acid changes may operate. Evidence is also presented for the generation of diversity through intragenic recombination with switching of corresponding variable domains between alleles. Recombination to exchange variable domains appears to occur throughout the length of the gene sequence, and has the potential to generate a mosaic pattern of diversity.

Molecular characterisation of the Theileria buffeli/orientalis group

Benign bovine Theileria parasites known as either Theileria buffeli, Theileria orientalis or Theileria sergenti are classified on basis of their morphology, vector specificity, pathogenicity and 18S small subunit ribosomal RNA or major piroplasm protein (MPSP) sequences. Since most isolates have been characterized on only some of these criteria and the existing confusion in nomenclature, an analysis was performed on eight different isolates to combine 18S rRNA data with MPSP data and the results were compared with available biological parameters. A polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) approach for both genes was used in combination with reverse line blot hybridisation for the 18S rRNA gene. Both MPSP and 18S rRNA genes were cloned and sequenced from parasites displaying aberrant MPSP RFLP profiles. Phylogeny based on published and determined 18S rRNA and MPSP sequences did correlate within the same isolate but there was no obvious correlation between molecular and biological data. Based on these findings, we suggest that the appropriate name for all these parasites is Theileria buffeli. A more specific nomenclature should be assigned when new molecular markers may become available.

Development of an indirect Tams1 enzyme-linked immunosorbent assay for diagnosis of Theileria annulata infection in cattle

An enzyme-linked immunosorbent assay (ELISA) was developed based on a recombinant major Theileria annulata merozoite surface antigen, Tams1. Four different recombinant proteins derived from two different Tams1 alleles, both in two different truncated forms, were tested for their performance in the ELISA. Furthermore, antigen concentration, various buffers, washing protocol, and the choice of anti-total-immunoglobulin G (IgG), anti-IgG1, or anti-IgG2 as second antibody were evaluated. The performance of the resulting ELISA was analyzed by measuring the coefficient of variation (CV). A total of 22 sera were analyzed over the measurement range, resulting in a CV of ca. 10%, whereas 30% variation is the maximum acceptable. The cutoff value was determined by the two-graph receiver operating characteristic (TG-ROC), using the indirect fluorescent antibody test (IFAT) as a reference. It was shown that up to 3 months postinfection (p.i.) IFAT is more sensitive and specific, whereas beyond 3 months p.i. ELISA performed as well as IFAT. The cutoff was determined at maximal sensitivity, based on the TG-ROC after 3 months p.i. Nine calves experimentally infected with four different T. annulata stocks remained positive in the ELISA for at least 1 year p.i. Finally, limited cross-reaction was found only with T. parva antisera, but not with any other Theileria or Babesia species. Since the T. parva endemic area hardly overlaps with T. annulata, the Tams1 ELISA has the potential to become a useful tool in the epidemiology of tropical theileriosis.

Babesia bovis and B. bigemina DNA detected in cattle and ticks from Zimbabwe by polymerase chain reaction

From blood collected from 94 cattle at 12 locations in the eastern and northeastern areas of Zimbabwe, DNA was extracted and analysed by polymerase chain reaction with primers previously reported to be specific for Babesia bigemina and Babesia borvis. Overall, DNA of Babesia bigemina was detected in the blood of 33/94 (35%) cattle and DNA from B. bovis was detected in 27/58 (47%) of cattle. The prevalence of DNA of B. bigemina was significantly higher in young animals (<2 years) (23/46) than in animals over 2 years of age (10/48; chi2= 8.77; P <0.01%). Although tick sampling was not thorough, Boophilus decoloratus could be collected at 7/9 sites sampled and Boophilus microplus at 4/9 sites. Of the 20 B. decoloratus allowed to oviposit before PCR analysis, 1 (5%) contained DNA that could be amplified with primers for B. bigemina while 12 (60%) were positive with primers for B. bovis. Of the B. microplus allowed to oviposit, 11/16 (69%) were positive for B. bovis DNA by PCR and 2/16 (12%) were positive for B. bigemina.

[Tick-borne fever (Ehrlichia phagocytophila infection) on a dairy farm in Friesland]

Disease outbreaks, associated with ixodid ticks, among cows on a dairy farm in Friesland, in the north of the Netherlands, were monitored during the summers of 1996, 1997, and 1998. The most important symptoms were a sudden drop in milk yield, fever, apathy, and problems with locomotion. The diagnosis 'tick-borne fever' was confirmed by finding Ehrlichia phagocytophila inclusion bodies in neutrophils of blood smears from sick animals. Significant economic losses due to the disease were recorded each year. Borrelia burgdorferi, although transmitted by the same tick, did not seem to be involved. Further research on tick-borne fever is of particular relevance in connection with recent E. phagocytophila cases diagnosed in dogs and in a human patient in the Netherlands.

Cowdria ruminantium antibodies in acaricide-treated and untreated cattle exposed to Amblyomma variegatum ticks in The Gambia

An indirect enzyme-linked immunosorbent assay (ELISA), based on the major antigenic protein I fragment B (MAPI-B) of Cowdria ruminantium, was used to assess seroprevalence in cattle in The Gambia. Two groups of 20 N'Dama and 20 Gobra zebu cattle were monitored for 12 months with flumethrin treatment and for another 10 months without acaricidal treatment. Two groups of 20 N'Dama and 20 Gobra cattle served as untreated controls. During the period of acaricidal treatment, the cumulative proportions of positive serum samples were 25.6 +/- 5.6% (+/- confidence interval) and 34.7 +/- 6.8% in treated N'Dama and Gobra cattle respectively; the proportion of positive sera in untreated cattle was 52.2 +/- 6.9% in N'Damas and 61.4 +/- 7.3% in Gobras. Within breed, difference in antibody prevalence between treated and untreated cattle was significant (P < 0.001) but between breed differences were not significant. In the 10 months following suspension of acaricide application, there was an increase of proportion of positive serum samples in previously treated N'Dama and Gobra cattle. In both previously treated and untreated animals the peak of positive seroreactions occurred during and subsequent to the period of activity of Amblyomma variegatum adults. Cumulative seroprevalences in previously treated N'Dama and Gobra cattle were 32.6 +/- 6.9% and 44.7 +/- 8.5%, respectively; in untreated animals seroprevalence was 38.6 +/- 7.2% in N'Dama and 65.3 +/- 8.4% in Gobra cattle. Throughout the study period, within the N'Dama breed, the seropositive rate in previously treated cattle did not differ from that in untreated animals. Conversely, within the Gobra breed, the number of positive seroreactions was higher (P < 0.002) in untreated animals than in previously treated cattle. These results provide a support for designing A. variegatum and heartwater control strategies, if necessary, in The Gambia in relation to cattle breeds.

Molecular detection of pathogen DNA in ticks (Acari: Ixodidae): a review

Ticks play an important role in human and veterinary medicine, in particular due to their ability to transmit a wide spectrum of pathogenic micro-organisms of protozoal, rickettsial, bacterial and viral origin. Pathogens in ticks can be identified by conventional methods such as indirect immunofluorescence, isolation in cell culture or by using histological staining techniques. However, the advent of the polymerase chain reaction (PCR) has resulted in tremendous improvements in the specific and sensitive detection of pathogen DNA in ticks. In this paper, literature on DNA extraction methods, PCR protocols, primers and probes, which are in use for the successful detection and identification of pathogens in ticks, are critically reviewed. Some recommendations are also given towards the end of this review.

Ticks feeding on humans: a review of records on human-biting Ixodoidea with special reference to pathogen transmission

In this article, literature records of argasid and ixodid ticks feeding on humans worldwide are provided in view of increased awareness of risks associated with tick bites. Ticks can cause paralyses, toxicoses, allergic reactions and are vectors of a broad range of viral, rickettsial, bacterial and protozoan pathogens. Approximately 12 argasid species (Argas and Ornithodos) are frequently found attached to humans who intrude into tick-infested caves and burrows. Over 20 ixodid tick species are often found on humans exposed to infested vegetation: four of these are Amblyomma species, 7 Dermacentor spp., 3 Haemaphysalis spp., 2 Hyalomma spp. and 6 Ixodes species. Personal protection methods, such as repellents and acaricide-impregnated clothing are advised to minimize contact with infected ticks. Acaricidal control of ixodid ticks is impractical because of their wide distribution in forested areas, but houses infested with soft ticks can be sprayed with acaricidal formulations. Attached ticks should be removed without delay. The best way is to grasp the tick as close to the skin as possible with fine tweezers and pull firmly and steadily without twisting. Finally, despite the fact that most people who are bitten destroy the offending tick in disgust, it is recommended that they preserve specimens in ethanol for taxonomic identification and detection of pathogens by molecular methods.

Identification of Theileria buffeli/orientalis and Babesia bigemina in Apulian cattle using molecular techniques and study of changes in blood parameters

Recently several cases of theileriosis due to the haemoprotozoan Theileria buffeli/orientalis have been recorded in the Apulian region, Italy. In this area other tick-borne pathogens were usually identified such as Anaplasma marginale and Babesia bigemina. Outbreaks were recorded showing that these pathogens can be observed separately or in mixed infections. Sub-clinical cases and carrier animals were also previously identified. A lack of specific techniques could not rule out the presence of other haemoparasites such as T. annulata, B. divergens, B. bovis, Ehrlichia phagocytophila and E. bovis. Moreover little is known about the tick species involved in the dissemination of these diseases. Therefore more powerful techniques to specifically identify Theileria or Babesia species have been recently developed. A PCR technique and reverse line blotting (RLB) system to specifically identify six Theileria species and three Babesia species were used. T. buffeli/orientalis and B. bigemina were the only pathogens observed in the targeted animals. The authors also present some changes in blood parameters for the animals followed during this study.

Integrated control of ticks and tick-borne diseases

Integrated control of ticks and tick-borne diseases (ICTTD) is currently promoted by an international project, supported by the European Union, with the aim to increase livestock productivity through the development of improved strategies for tick control, vaccine delivery and integrated diagnostics for tickborne diseases. This paper gives a brief overview of the ICTTD project activities against the background of recent initiatives to assess the impact of ticks and tick-borne diseases in the Mediterranean region.

Molecular characterization of ticks and tick-borne pathogens

Ticks and their vertebrate hosts often carry several pathogens simultaneously, which either belong to different or to the same genera. Conventional methods (such as blood smear examination or tick salivary gland staining) are often unable to discriminate between pathogens. Therefore, molecular methods for the detection and differentiation of tick-borne pathogens are increasingly used. Technical problems still remain to identify pathogens within tick tissues, or within host animals when infection rates are very low. Recently we developed an integrated approach to identify several pathogens with only one molecular test. This approach, the reverse line blot hybridization (RLB) reduces costs of analysis, gives quicker results. and allows standardized inter-laboratory comparisons. Finally, this paper also focuses on the molecular diagnostic techniques currently used in the laboratories of the Mediterranean countries.

Evaluation of recombinant sporozoite antigen SPAG-1 as a vaccine candidate against Theileria annulata by the use of different delivery systems

The major sporozoite surface antigen of Theileria annulata (SPAG-1) is a candidate for inclusion in a subunit vaccine. In this paper we summarize the results of 4 vaccination experiments using recombinant SPAG-1 expressed in different systems and presented in different adjuvants. The antigen has been presented as either a C terminal 108 amino acid peptide (called SR1) expressed as both beta-galactosidase and hepatitis B core antigen fusions or as a full-length form expressed as a GST fusion with an N terminal His6 tag. We used different adjuvants, namely Freund's, saponin, ISCOMs and a proprietary adjuvant supplied by SmithKline Beecham, which we call SKBA. The data point to the conclusion that SPAG-1 can elicit partial protection and is therefore suitable for inclusion in an eventual multicomponent subunit vaccine.

Protective immune mechanisms to ticks and tick-borne diseases of ruminants

A workshop of the European Union (EU) Concerted Action Project on the Integrated Control of Ticks and Tick-borne diseases (CA-ICTTD) recently assessed protective immune mechanisms to ticks and tick-borne diseases. The consensus achieved there is summarized here by Patricia Preston and Frans Jongejan. The current understanding of this field is expanded upon by the accompanying articles, and Poster, in this special issue of Parasitology Today.